Internet-of-Things (IoT)
Summer Engineering Program 2018
University of Notre Dame
LAB COMPONENT

Setting Up Python
Jupyter Notebook:
https://jupyter.readthedocs.io/en/latest/install.ht
ml
IDLE: Integrated Development and Learning
Environment

Python 101
• Unlike C/C++ or Java, Python statements do not
end in a semicolon
• In Python, indentation is the way you indicate
the scope of a conditional, function, etc.
• Look, no braces!
• Python is interpretive, meaning you don’t have
to write programs
• You can just enter statements into the Python
environment and they’ll execute

Python 101
• As in every language, a variable is the name of a
memory location
• Python is weakly typed, i.e., you don’t declare
variables to be a specific type
• A variable has the type that corresponds to the value
you assign to it
• Variable names begin with a letter or an underscore
and can contain letters, numbers, and underscores
• Python has reserved words that you can’t use as
variable names

Python 101
At the >>> prompt, do the following:
x=5
type(x)
x=“this is text”
type(x)
x=5.0
type(x)

Python 101
• You’ve already seen the print statement
• You can also print numbers with formatting
– [flags][width][.precision]type
– print (”pi: {0:8.2f}”.format(3.141592))
• These are identical to Java or C format specifiers

Python 101
• All code should contain comments that describe
what it does
• In Python, lines beginning with a # sign are
comment lines
• You can also have comments on the same line as
a statement
# This entire line is a comment
x=5 # Set up loop counter

Python 101
• Arithmetic operators we will use:
– + - * / addition, subtraction/negation,
multiplication, division
– % modulus, a.k.a. remainder
– ** exponentiation
• Precedence: Order in which operations are
computed.
– * / % ** have a higher precedence than + -
1 + 3 * 4 is 13
– Parentheses can be used to force a certain order of
evaluation.
(1 + 3) * 4 is 16

Python 101
• When integers and reals are mixed, the result is a
real number.
–Example: 1 / 2.0 is 0.5
–The conversion occurs on a per-operator basis.
– 7 / 3 * 1.2 + 3 / 2
– 2 * 1.2 + 3 / 2
– 2.4 + 3 / 2
– 2.4 + 1
– 3.4

Python 101
• Use this at the top of your program: from math
import *

Python 101
• Many logical expressions use relational
operators:

Python 101
• These operators return true or false

Python 101
• Syntax:
if <condition>:
<statements>
x = 5
if x > 4:
print(“x is greater than 4”)
print(“This is not in the scope of the
if”)

Python 101
• The colon is required for the if
• Note that all statements indented by one level
below the if are within it scope:
x = 5
if x > 4:
print(“x is greater than 4”)
print(“This is also in the scope of
the if”)

Python 101
if <condition>:
<statements>
else:
<statements>
• Note the colon following the else
• This works exactly the way you would expect

Python 101
• Syntax for “for” statement:
for variableName in groupOfValues:
<statements>
• variableName gives a name to each value, so you can
refer to it in the statements
• groupOfValues can be a range of integers, specified
with the range function
• Example:
for x in range(1, 6):
print x, "squared is", x * x

Python 101
The range function specifies a range of integers:
range(start, stop)- the integers between start
(inclusive) and stop (exclusive)
It can also accept a third value specifying the
change between values:
range(start, stop, step)- the integers
between start (inclusive) and stop (exclusive) by
step

Python 101
• “While:” executes a group of statements as long as a
condition is True
• Good for indefinite loops (repeat an unknown number of
times)
• Syntax:
while <condition>:
<statements>
• Example:
number = 1
while number < 200:
print number,
number = number * 2

Exercise
• Write a Python program to compute and display
the first 16 powers of 2, starting with 1

Strings
• String: A sequence of text characters in a
program
• Strings start and end with quotation mark " or
apostrophe ' characters
• Examples:
"hello"
"This is a string"
‘This, too, is a string. It can be very long!’

Strings
• A string can represent characters by preceding
them with a backslash
– t tab character
– n new line character
– " quotation mark character
– backslash character
• Example: "HellottherenHow are you?"

Strings
• As with other languages, you can use square
brackets to index a string as if it were an array:
name = “Arpita Nigam”
print(name, “starts with “, name[0])

Strings
• len(string) - number of characters in a
string
• str.lower(string) - lowercase version of a string
• str.upper(string) - uppercase version of a string
• str.isalpha(string) - True if the string has
only alpha chars
• Many others: split, replace, find, format, etc.
• Note the “dot” notation: These are static methods

Byte Arrays and Strings
• Strings are Unicode text and not mutable
• Byte arrays are mutable and contain raw bytes
• For example, reading Internet data from a URL
gets bytes
• Convert to string:
cmd = response.read()
strCmd = str(cmd)

Other Built-In Types
• Tuples, lists, sets, and dictionaries
• They all allow you to group more than one item
of data together under one name
• You can also search them

Tuples
• Unchanging sequences of data
• Enclosed in parentheses:
tuple1 = (“This”, “is”, “a”, “tuple”)
print(tuple1)
• This prints the tuple exactly as shown
print(tuple1[1])
• Prints “is” (without the quotes)

Lists
• Changeable sequences of data
• Lists are created by using square brackets:
breakfast = [ “coffee”, “tea”, “toast”, “egg”
]
• You can add to a list:
breakfast.append(“waffles”)
breakfast.extend([“cereal”, “juice”])

Dictionaries
• Groupings of data indexed by name
• Dictionaries are created using braces
sales = {}
sales[“January”] = 10000
sales[“February”] = 17000
sales[“March”] = 16500
food = {"ham" : "yes", "egg" : "yes", "spam" :
"no"}
food
food[“ham”]
food[“egg”] = ‘no’

Sets
• Sets are similar to dictionaries in Python, except
that they consist of only keys with no associated
values
• Essentially, they are a collection of data with no
duplicates
• They are very useful when it comes to removing
duplicate data from data collections.

Writing Functions
• Define a function:
def <function name>(<parameter list>)
• The function body is indented one level:
def computeSquare(x)
return x * x
# Anything at this level is not part of the
function

Error Handling
• Use try/except blocks, similar to try/catch:
fridge_contents = {“egg”:8, “mushroom”:20,
“pepper”:3, “cheese”:2, “tomato”:4,
“milk”:13}
try:
if fridge_contents[“orange juice”] > 3:
print(“Let’s have some juice!”)
except KeyError:
print(“Awww, there is no orange juice.”)

Error Handling
• Note that you must specify the type of error
• Looking for a key in a dictionary that doesn’t
exist is an error
• Another example:
try:
sock = BluetoothSocket(RFCOMM)
sock.connect((bd_addr, port))
except BluetoothError as bt
Print(“Cannot connect to host: “ +
str(bt))

File I/O
• You can read and write text files in Python much
as you can in other languages, and with a similar
syntax
• To open a file for reading:
try:
configFile = open(configName, "r")
except IOError as err:
print(“could not open file: “ + str(err))

File I/O
• To read from a file:
while 1:
line = configFile.readline()
if len(line) == 0:
break

File I/O
• You can also read all lines from a file into a set,
then iterate over the set:
lines = file.readlines()
for line in lines:
print(line)
file.close()

File I/O
• Writing to a text file
file=open(‘test.txt’,”w”)
file.write(“This is how you create a new text
file”)
file.close()
with open('/etc/passwd') as f:
for line in f:
print(line)

Assignment 1: Task 1
stock = { "banana": 6,
"apple": 0,
"orange": 32,
"pear": 15 }
prices = { "banana": 4,
"apple": 2,
"orange": 1.5,
"pear": 3 }
Write a function “Rechnung” (bill) that takes a list of foods (e.g.,
["banana", "orange", "apple"]) as input and computes the total
price (only for items in stock) and adjusts the stock accordingly.
Write the bill computation as function that takes one parameter
(list of foods).

Assignment 1: Task 2
Continue Task 1 by writing the shopping list into a
newly created file, each item in a new line. Then
write a second program that reads the file in a
loop, line by line and prints each line.

Feierabend